1. Field of the Invention
The present invention relates to an image processor, an image processing method, and an image processing program.
2. Description of the Related Art
Conventionally, when a monochrome document is read in binary, especially, a picture portion and a shaded portion in the document are not reproduced. When the monochrome document is read in color, color components which are not present in the document are output due to scanner characteristics, and a file size becomes large.
Then, a user obtains an image in which the picture portion and the shaded portion are reproduced, without color components, and having a small file size, by switching a reading mode to gray setting to read the monochrome document.
JP-A-11-191832 discloses a technique to perform a main scan after distinguishing an image type (color, gray or binary) by a pre-scan. JP-A-2007-81687 discloses a technique to determine contents (color, gray or binary, and resolution) of a document image by the pre-scan and set a reading condition of front and back sides. JP-A-8-242366 discloses a technique to detect a document attribution (color, gray or binary and resolution) and switch the reading mode based on the detected document attribution. JP-A-2002-57822 discloses a technique to change the reading mode when a reading size is larger than a free space of a disk and inform the user of the same.
However, there is a problem that a reading speed is reduced, because it is required to read the document twice in the pre-scan and the main scan in JP-A-11-191832, it is required to read the document in the pre-scan in JP-A-2007-81687, and it is required to return the document and read again depending on the detection result in JP-A-8-242366. In JP-A-2007-81687, it is possible to configure the read setting of the front and back sides in the scanner capable of continuously feeding paper; however, there is a problem that the read setting of a first piece of paper may not be changed or that the read setting of the first piece of paper and a second piece of paper may not be different. In JP-A-8-242366, a histogram is used when determining multiple values or binary by a document attribution; however, there is a problem that when using the histogram, the character or the like also seems gray in determination with low resolution, so that it is difficult to determine with high accuracy.